Dynamometers measure force or power, and are often used for diagnostic testing of machinery, such as automobiles. One type of dynamometer often used for testing of automobiles is known as a chassis dynamometer. A chassis dynamometer generally includes at least one roller or drum that supports the drive wheels of an automobile to be tested and a sensor associated with the roller. The automobile drives the roller, while the sensor detects roller properties, such as rotational speed or acceleration.
A chassis dynamometer may include multiple rollers. For example, rollers may be provided for the automobile's front and rear wheels for use with all wheel drive automobiles, in which the front and rear wheels must rotate at the same time. In such dynamometers, it may be desirable for the front and rear rollers' rotation to be synchronized, in order to test the vehicle under realistic driving conditions. It may also be desirable for such a dynamometer to permit adjustment of the distance between the front and rear rollers to accommodate automobiles having different wheelbases.